Many plants enter our homes for the holidays as we deck the halls with holly boughs and adorn an evergreen tree. Perhaps one of the most interesting botanical holiday traditions, though, is kissing under the mistletoe.

Mistletoe has long been a part of human folklore and tradition. In Europe, the Druids and other ancient peoples believed that mistletoe possessed supernatural powers because it remained green in winter when the trees lost their leaves. Because of this, the Druids used mistletoe for sacred rituals during the winter solstice.

Today we recognize mistletoe as a sprig of greenery with spoon-shaped leaves and white berries, tied up with ribbon during holiday festivities. Washington Irving wrote about the kissing tradition in 1820 in The Sketchbook of Geoffrey Crayon, Gent: "The mistletoe is still hung up in farm-houses and kitchens at Christmas, and the young men have the privilege of kissing the girls under it, plucking each time a berry from the bush. When the berries are all plucked the privilege ceases."

Outside of its use as holiday decor, the existence of mistletoe is rarely considered. In nature, it grows not on the ground, but high in the branches of trees. One species of mistletoe, Phoradendron leucarpum, is native to southern Illinois.

The scientific name Phoradendron translates to "thief of the tree." This name is apt, as mistletoe is a hemiparasitic plant that steals water and nutrients from the tree that it lives on. Because mistletoe depends upon a host for survival, it requires a specialized dispersal mechanism that delivers seeds to tree branches.

Mistletoe berries, while toxic to humans, are a prized food source for birds. However, simply being eaten by a bird and excreted in midair, only to fall to the ground, would not do. Instead, mistletoe seeds have a sticky coating that causes them to cling to bird feathers and feet after being passed. The bird must land and scrape these sticky seeds off onto another surface like a twig, thus delivering them to their desired destination with great frequency.

Named for its seed, the word "mistletoe" is derived from two Anglo-Saxon words that meant dung and twig. It is both ironic and beautiful that a parasitic plant called "dung on a twig" can be a symbol of love and vitality. I hope this brief botanical history lesson gives you a new appreciation for mistletoe this season.